BIOCIDAL ACTIVITY OF A PEROXIDASE-CATALYZED SANITIZER AGAINST SELECTED BACTERIA ON INERT CARRIERS AND EGG SHELLS

Microbial contamination of table eggs has become an important public health problem. In this study, peroxidase-catalyzed compound (PCC), which is innocuous to humans, was tested for its bactericidal activity on a variety of bacteria on inert carriers and on egg shell surfaces. When inert carriers containing Salmonella choleraesuis, Staphylococcus aureus and Pseudomonas aeruginosa were exposed to PCC, population reductions were within acceptable performance standards for standard and simulated hard water conditions. When evaluated for sporicidal activity, PCC gave no positive carriers in a total of 60 carriers tested for either Bacillus subtilis or Clostridium sporogenes. Enterococcus faecalis and Pseudomonas fluorescens viable cells on egg shell surfaces were determined after dip treatment with deionized distilled water, PCC or chlorine-treated (200 ppm) water for 1, 3 and 5 min and compared with those of a control without dip treatment. All treatments significantly reduced the viable cells (log₁₀ CFU/egg) compared to controls for both strains (p < 0.05). Populations of both strains surviving chlorine and PCC were significantly lower than surviving deionized-distilled water, although PCC gave higher recoveries than chlorine (p < 0.05). Populations exposed to PCC treatment were significantly decreased after 3 and 5 min, respectively (p < 0.05). The results of this study indicate that PCC has potential as a table egg sanitizer that could replace the other egg sanitizers which may be environmentally problematic. Based on the inert carrier studies, PCC may also be an effective disinfectant for egg processing equipment and plastic egg cartons in the presence of hard water or contaminating soil .     

Reduction of Salmonella Contamination on Chicken Egg Shells by a Peroxidase-Catalyzed Sanitizer

A peroxidase-catalyzed compound (PCC) sanitizer was tested to determine its bactericidal activity on Salmonella typhimurium and Salmonella enteritidis inoculated on egg shell surfaces. Eggs with no treatment were compared to those immersed in either deionized distilled water, PCC or 200 ppm chlorine-treated water for 1, 3 or 5 min. Eggs immersed in PCC or chlorinated water solutions had lower (P < 0.05) S. typhimurium and S. enteritidis populations than those not exposed to treatments. No differences were detected among PCC and chlorine treatments except the S. typhimurium populations from PCC dipped eggs were significantly higher than those from eggs dipped in the chlorinated water for 1 min. Results indicate that PCC has potential as an effective shell egg sanitizer.     

COMPARISON OF CHLORINE WITH AN IODINE-BASED COMPOUND ON EGGSHELL SURFACE MICROBIAL POPULATIONS IN A COMMERCIAL EGG WASHER

Microbial contamination of egg shells is of great importance in the commercial production of table eggs. The objective of this project was to determine the effectiveness of an iodine-based disinfectant (IBD) on the microbial population of eggshell surfaces under simulated industry egg processing conditions with a commercial egg washer used as the delivery system for sanitizers. Recirculated egg washer water containing 3.69–5.81 log colony-forming units (CFU)/mL aerobic organisms and 2.02–2.47 g/L total dissolved solids (TDS) was obtained from a commercial egg processing facility and used to simulate conditions found in the commercial egg industry. Sanitizing treatments consisted of distilled deionized water (DDW), IBD, and chlorine (CL; 200 ppm). Enumeration of aerobic plate populations indicated that IBD and CL treatment significantly (p < 0.05) decreased microbial populations on the shell compared to DDW treatment when egg wash water TDS were lower (2.02 – 2.03 g/L) and wash water aerobic plate counts (APC) were higher (5.05 – 5.85 log CFU/mL). When egg wash water TDS was higher (2.47 g/L) and wash water APC were lower (3.69 log CFU/mL) sanitizers were not effective in reducing egg shell microbial populations. No difference in egg shell APC counts was detected between the IBD and CL. In a second trial, cycloheximide or tetracycline amendments were added to media to test the effectiveness of the treatments on either mold and fungi or bacteria alone. When wash water TDS were higher (2.44–2.46 g/L) the sanitizers were again less effective against bacteria compared to samples from lower TDS while fungal populations did not show any significant differences among the treatments. It was concluded from this study that the IBD is an effective sanitizer when used in conjunction with a commercial egg washer but potential efficacy is dependent on the level of TDS in the egg wash water.     

Efficacy of electrolyzed water in inactivating Salmonella enteritidis and Listeria monocytogenes on shell eggs

The efficacy of acidic electrolyzed (EO) water produced at three levels of total available chlorine (16, 41, and 77 mg/ liter) and chlorinated water with 45 and 200 mg/liter of residual chlorine was investigated for inactivating Salmonella Enteritidis and Listeria monocytogenes on shell eggs. An increasing reduction in Listeria population was observed with increasing chlorine concentration from 16 to 77 mg/liter and treatment time from 1 to 5 min, resulting in a maximal reduction of 3.70 log CFU per shell egg compared with a deionized water wash for 5 min. There was no significant difference in antibacterial activities against Salmonella and Listeria at the same treatment time between 45 mg/liter of chlorinated water and 14-A acidic EO water treatment (P > or = 0.05). Chlorinated water (200 mg/liter) wash for 3 and 5 min was the most effective treatment; it reduced mean populations of Listeria and Salmonella on inoculated eggs by 4.89 and 3.83 log CFU/shell egg, respectively. However, reductions (log CFU/shell egg) of Listeria (4.39) and Salmonella (3.66) by 1-min alkaline EO water treatment followed by another 1 min of 14-A acidic EO water (41 mg/liter chlorine) treatment had a similar reduction to the 1-min 200 mg/liter chlorinated water treatment for Listeria (4.01) and Salmonella (3.81). This study demonstrated that a combination of alkaline and acidic EO water wash is equivalent to 200 mg/liter of chlorinated water wash for reducing populations of Salmonella Enteritidis and L. monocytogenes on shell eggs.     

Variations in external and internal microbial populations in shell eggs during extended storage

The current project was conducted to determine the microbial quality of commercially processed shell eggs during extended storage. Unwashed eggs were collected at the accumulator before entering the processing line. Washed eggs were retrieved after placement in flats. All eggs were stored on pulp flats at 4 degrees C for 10 weeks. Twelve eggs from each treatment were rinsed on the day of collection and during each week of storage. After rinsing, eggs were sanitized in ethanol, and contents were aseptically collected. Total aerobes, yeasts and molds, Enterobacteriaceae, and pseudomonads were enumerated from shell rinses and pooled egg contents. During storage, no differences were found between unwashed and washed eggs for Enterobacteriaceae and pseudomonads in either shell rinses or contents. No differences were found between treatments for population levels of total aerobes or yeasts and molds in the egg contents throughout the storage period. Significant differences between treatments were found at each week of storage for external shell contamination by total aerobes. The highest unwashed egg contamination occurred at week 8 of storage and the lowest was at weeks 0 and 1 of storage. The highest shell contamination with aerobic bacteria on the washed eggs was found at week 0 of storage and the lowest was at week 7. Yeast and mold contamination determined by shell rinses was also significantly different between treatments at each week of storage. Commercially washed eggs were significantly less contaminated than were unwashed eggs for the populations monitored.     

Modelling the inactivation of Listeria monocytogenes and Salmonella typhimurium in simulated egg wash water

The inactivation of Listeria monocytogenes Scott A and Salmonella typhimurium in synthetic egg washwater was studied under varying conditions of temperature (38°C to 46°C), egg solids (0%, 2%), pH (9·5 to 10·5) and chlorine concentration (0 to 10 μg ml^-1 [ppm]) using a full factorial design. Survival was measured as the logarithm of the time required for a 4-log reduction in viable counts. Both pathogens were significantly affected by temperature and the presence of egg, while the survival of S. typhimurium was significantly reduced by pH and chlorine alone. Both pathogens were affected by second order interactions involving egg and either pH or chlorine. Egg was the most significant factor, reducing the survival of L. monocytogenes while promoting the survival of S. typhimurium. Two linear equations were derived to describe the decrease in survival of L. monocytogenes and S. typhimurium as a function of the 4 factors. These equations were used to estimate conditions which would reduce the time for a 4-log reduction in viable counts to <30 min. In the absence of egg solids, chlorine (20 μg ml^-1) can be used to control L. monocytogenes and S. typhimurium using moderate temperature (42°C) and pH (10·5). When egg is present in wash water, increased temperature (47·4°C) and pH (10·8) are required.     

Impact of commercial processing on the microbiology of shell eggs

Shell egg microbiology has been studied extensively, but little information is available on how modern U.S. processing conditions impact microbial populations. As regulations are being drafted for the industry, such information can be important for determining processing steps critical to product safety. Five different shell egg surface microbial populations (aerobic bacteria, yeasts and molds, Enterobacteriaceae, Escherichia coli, and Salmonella) were monitored at 12 points along the processing line (accumulator, prewash rinse, washer 1, washer 2, sanitizer, dryer, oiler, scales, two packer head lanes, rewash entrance, and rewash exit). Three commercial facilities were each visited three times, a total of 990 eggs were sampled, and 5,220 microbiological samples were subsequently analyzed. Although variations existed in concentrations of microorganisms recovered from each plant, the patterns of fluctuation for each population were similar at each plant. On average, aerobes, yeasts and molds, Enterobacteriaceae, and E. coli prevalence were reduced by 30, 20, 50, and 30%, respectively, by the end of processing. The microbial concentrations (log CFU per milliliter) in the egg rinse collected from packer head lanes were decreased by 3.3, 1.3, 1.3, and 0.5, respectively, when compared with those of rinses collected from eggs at the accumulator. Salmonella was recovered from 0 to 48% of pooled samples in the three repetitions. Higher concentrations of Salmonella were recovered from preprocessed than from in-process or ready-to-pack eggs. These data indicate that current commercial practices decrease microbial contamination of egg shell surfaces.     

Eggshell factors influencing eggshell penetration and whole egg contamination by different bacteria, including Salmonella enteritidis

Trans-shell infection routes and whole egg contamination of 7 selected bacterial strains; Staphylococcus warneri, Acinetobacter baumannii, Alcaligenes sp., Serratia marcescens, Carnobacterium sp., Pseudomonas sp. and Salmonella enteritidis, recovered from egg contents, were studied. The first objective was to correlate bacterial eggshell penetration with various eggshell characteristics and bacterial strains. An agar approach was used to assess the eggshell penetration. The second objective was to assess the contamination of whole eggs with the bacterial strains; whole intact eggs were used in this case. The intact shells of agar-filled and whole eggs were inoculated with 10(3) -10(4) cfu of the selected strains. During 3 weeks storage at 20 degrees C and 60% relative humidity, the bacterial eggshell penetration was regularly monitored. The whole egg contamination was only analyzed after 3 weeks. The eggshell characteristics such as area eggshell, shell thickness and number of pores did not influence the bacterial eggshell penetration. For each individual bacterial strain the mean cuticle deposition was lower for penetrated compared to non-penetrated eggshells. For the individual strain Carnobacterium sp. and for the global results of all strains this difference was statistical significantly. The whole egg contamination was not influenced by neither the area of the eggshell nor the porosity of the eggshell. The results of the agar approach indicate that the Gram-negative, motile and non-clustering bacteria penetrated the eggshell most frequently; Pseudomonas sp. (60%) and Alcaligenes sp. (58%) were primary invaders followed by S. enteritidis (43%). All selected strains were able to penetrate; penetration was observed most frequently after ca. 4-5 days. Particularly S. enteritidis was a primary invader of whole eggs: the membranes and/or the content of 32% of the whole eggs was contaminated. The remaining bacterial eggshell contamination with the selected strain was determined after 3 weeks storage. Penetrated eggshells and contaminated whole eggs showed a significantly higher bacterial contamination on the eggshell compared to non-penetrated eggshells and non-contaminated whole eggs respectively (global results of all strains). The influence of hen age on bacterial eggshell penetration and egg content contamination was not significant. While the agar approach is suitable to study the influence of the eggshell characteristics on the bacterial eggshell penetration, the intact egg approach gives an estimation of the penetration of the shell followed by the probability of survival and migration in whole eggs.     

An assessment of the microbiological risks involved with egg washing under commercial conditions

The potential benefits of washing eggs is offset by a historical perception in the European Union that wetted eggs are prone to spoilage and water loss. This study describes the effects of spray jet washing under various processing conditions to shell surface counts of Salmonella and the presence of bacteria in egg contents. Experiments used eggs that were contaminated with Salmonella Enteritidis PT4 or Salmonella Typhimurium DT104 before cuticle hardening. Washing of contaminated eggs under optimum conditions resulted in a more than 5-log reduction of Salmonella counts from the shell surface. Salmonella was not isolated from the yolk or albumen of any egg washed by the optimal protocol, suggesting that when properly controlled, egg washing did not cause Salmonella to enter the contents. However, contamination did arise if strict control was not maintained over the wash and rinse water temperatures. Both Salmonella Enteritidis and Salmonella Typhimurium were shown to enter the egg contents when water temperatures were lowered, indicating that strict temperature control must be maintained in order to prevent the ingress of Salmonella into egg contents. Other washing machine parameters that were investigated did not significantly affect Salmonella entry into the egg contents but influenced shell surface kill levels to varying degrees.     

Effect of chlorine, sodium chloride, trisodium phosphate, and ultraviolet radiation on the reduction of Yersinia enterocolitica and mesophilic aerobic bacteria from eggshell surface

Eggshell sanitizing practices are necessary to improve microbiological safety of fresh hen eggs and their products. In this work, the effects of 100 mg/liter free chlorine (chl), 3% sodium chloride (NaCl), 1, 5, and 12% trisodium phosphate (TSP) in wash solutions, and UVR (ultraviolet radiation; 4.573 microW/cm2) were studied at different times on uninoculated and Yersinia enterocolitica-inoculated eggs. On uninoculated eggs, the best results were obtained with 100 mg/liter chlorine and UV exposure for >25 min, with reductions of 1.28 and 1.60 log cycles, respectively, compared to the average bacterial count (4.55 log CFU/egg) on the control (untreated eggs). On Y. enterocolitica-inoculated eggs, highest reductions of the average bacterial count (7.35 log CFU/egg) were obtained with 5 and 12% TSP and 100 mg/liter chl. The decrease obtained with 12% TSP (3.74-log reduction) was significantly higher (P < 0.05) than those obtained with the remaining treatments. Y. enterocolitica was more resistant to UVR than the eggshell natural mesophilic aerobic microflora, except when low inoculum (4.39 log CFU/egg) was assayed. Changes in eggshell microstructure were measured by the blue lake staining method. The presence of Yersinia and Salmonella in eggshell natural flora was also investigated.     

Survival of Yersinia enterocolitica and mesophilic aerobic bacteria on eggshell after washing with hypochlorite and organic acid solutions

Populations of Yersinia enterocolitica 0:9 and mesophilic aerobic bacteria on the shell of fresh chicken eggs were assessed prior and after washing with 0.75%, 1%, and 3% acetic and lactic acids, 50, 100, and 200 mg/liter (ppm) of chlorine, and water. Highest reductions of mesophilic aerobic bacterial populations (normal flora) on trypticase soy agar were 1.28 and 2.15 log10 cycles with 100 and 200 mg/liter of chlorine, 0.28 and 0.36 log10 cycles with 1% and 3% acetic acid, and 0.70 and 0.71 log10 cycles with 1% and 3% lactic acid, respectively, as compared to the control group. No Salmonella or Yersinia were detected among the natural flora of the eggs. On Y. enterocolitica O:9-inoculated eggs, reductions of 2.66, 2.77, and 2.92 log10 cycles by 50, 100, and 200 mg/liter of chlorine, of 2.47, 2.48, and 2.49 log10 cycles by 0.75%, 1%, and 3% of acetic acid, and of 2.48 and 2.72 log10 cycles with 1% and 3% of lactic acid, respectively, were observed with respect to the control. Organic acids at 3% caused detachment of the surface cuticle of the eggshell. Y. enterocolitica was more sensitive to the wash treatments than the natural microflora. The absence of potentially pathogenic Y. enterocolitica, observed for other fresh foods, should be a norm for fresh eggs sold in retail stores.     

A machine vision system for identification of micro-crack in egg shell

Cracks or micro-cracks present in chicken egg shell are sources of bacterial contamination which has adverse effect to consumer’s health. One egg system vacuum pressure chamber was fabricated to force open the micro-crack in egg shell and machine vision system was developed to acquire the image. Vacuum pressure of 18 kPa was applied to force open the crack. Two hundred chicken eggs ranging in color from white to brown, intact and cracked, dirty and clean were collected as samples. A robust algorithm was developed to extract the micro-crack from the image without being affected by the presence of dirt in the egg shell. The developed system was able to detect the micro-crack with 100% accuracy without being influenced by the presence of dirt in the egg shell. The developed system can be a milestone for developing egg sorting machines on the basis of presence-absence of crack in egg shell.     

二氧化氯在鲜蛋消毒保鲜中的应用研究

以新鲜鸡蛋为原料,研究二氧化氯对其进行处理后消毒保鲜的效果。经挑选、分级后,分别将鸡蛋置于浓度为30、40、50mg/L的ClO2溶液中,各浸泡5、10、15min,另取二氧化氯浓度为50mg/L浸泡10min的处理组置于密封袋中为密封袋组,未做任何处理的鸡蛋设为对照组。所有实验组均在室温条件下贮藏,分别在第10、20、30、40d测定鸡蛋的失重率、蛋黄系数、哈夫值、挥发性盐基氮等指标。结果表明,二氧化氯对鸡蛋蛋壳有很好的灭菌作用,对鸡蛋的保鲜效果不显著,消毒后置于密封袋中的鸡蛋保鲜效果较好。     

Pathogen prevalence and microbial levels associated with restricted shell eggs

Restricted shell eggs that do not meet quality standards for retail but maintain acceptable quality for inclusion in further processed eggs are often diverted to further processing. A study was conducted to characterize the microbiological populations present on and in these eggs. On a single day, restricted eggs were collected from three shell egg processing plants a total of three times (replicates). Six shells or egg contents were combined to create a pool. Ten pools of shells and contents were formed for each plant per replicate. Shells and membranes were macerated in 60 ml of diluent. Contents were stomacher blended to form a homogeneous mixture. Total aerobic microorganisms and Enterobacteriaceae were enumerated. The prevalence of Salmonella, Campylobacter, and Listeria was determined by cultural methods. Average aerobic counts were 4.3 log CFU/ml for the shells and 2.0 log CFU/ml for the contents. There were plant x replicate differences for both (P < 0.05 and P < 0.01, respectively). The average Enterobacteriaceae level associated with the shell was 2.4 log CFU/ml and less than 0.1 log CFU/ml for the egg contents, with 36.7% of the samples being positive. One shell sample (0.5% of total samples) was Campylobacter positive. Two shell samples (1.1% of total samples) were Salmonella positive. Twenty-one percent of samples were positive for Listeria (33 shells and 5 contents). Although current pasteurization guidelines are based on Salmonella lethality, the results of this study reiterate the need to revisit the guidelines to determine the effectiveness for other pathogenic species.     

不同品种鲜蛋品质差异分析

目的探究褐壳蛋、粉壳蛋和白壳蛋3种类型鸡蛋的品质差异以及对于蛋粉加工的潜在影响。方法选用京红1号、京粉1号和京白1号所产的褐壳蛋、粉壳蛋和白壳蛋作为试验对象,对37周龄和51周龄蛋鸡所产3种类型鸡蛋的蛋品质进行分析比较。结果 37周龄和51周龄的白壳蛋蛋壳厚度、蛋壳比例和蛋壳强度均显著低于其他2个类型鸡蛋(P0.05);37周龄时3种类型鸡蛋的蛋黄水分含量没有显著性差异(P0.05);白壳蛋蛋清水分含量以及总水分含量均较其他2个类型鸡蛋要低。37周龄时褐壳蛋的蛋黄蛋白质和脂肪含量均显著高于其他2个品种,白壳蛋次之,粉壳蛋最低。37周龄时白壳蛋的蛋清蛋白质含量显著低于其他2个品种。由于蛋清中脂肪含量极少,本试验不予考虑。结论褐壳蛋加工成蛋粉后具有更好的营养价值,而白壳蛋可以提高蛋粉加工的产量。     

Thermal inactivation kinetics of Salmonella spp. within intact eggs heated using humidity-controlled air.

The heat resistance of six strains of Salmonella (including Enteritidis, Heidelberg, and Typhimurium) in liquid whole egg and shell eggs was determined. Decimal reduction times (D-values) of each of the six strains were determined in liquid whole egg heated at 56.7 degrees C within glass capillary tubes immersed in a water bath. D-values ranged from 3.05 to 4.09 min, and significant differences were observed between the strains tested (alpha = 0.05). In addition, approximately 7 log10 CFU/g of a six-strain cocktail was inoculated into the geometric center of raw shell eggs and the eggs heated at 57.2 degrees C using convection currents of humidity-controlled air. D-values of the pooled salmonellae ranged from 5.49 to 6.12 min within the center of intact shell eggs. A heating period of 70 min or more resulted in no surviving salmonellae being detected (i.e., an 8.7-log reduction per egg).     

Effect of sanitizing treatments on removal of bacteria from cantaloupe surface, and re-contamination with Salmonella

There are many reports of disease due to consumption of cantaloupes contaminated at the surface with enteric pathogens. Salmonella is among the most frequently reported cause of foodborne outbreaks of gastroenteritis in the United States. Research was undertaken to determine the effects of sanitizer and hot water treatments on microbial populations on cantaloupe surfaces and to determine whether prior decontamination of melons by sanitizer treatment affects vulnerability to recontamination by Salmonella. Cantaloupes were sanitized with 200 ppm chlorine or 2.5% hydrogen peroxide solution for 2 min, or hot water (96 degrees C) for 2 min and were held at 5 degrees C for 24 h. Hot water treatments reduced the microbial populations on cantaloupe surface by 4.9 log reduction while H2O2 or chlorine caused approximately 2.6 log unit reduction on cantaloupe surfaces. When sanitized or hot water treated whole cantaloupes were re-inoculated with Salmonella. Higher populations of Salmonella were recovered from sanitized cantaloupes than from the untreated controls; recovery was greater from hot water treated cantaloupes than from cantaloupes treated with chlorine or hydrogen peroxide. The results of this study clearly show that sanitized cantaloupes are susceptible to recontamination if exposed to a human bacterial pathogen during subsequent handling.     

Efficacy of disinfection of shell eggs externally contaminated with Salmonella enteritidis. Implications for egg testing.

Experimental contamination of the surface of shell eggs by dipping in a culture of Salmonella enteritidis resulted in the presence of Salmonella enteritidis in/on the shells as well as shell membranes but not in the egg content. Disinfection with Lugol's solution, chlorhexidine, ethanol, quarternary ammonium solutions or flaming after dipping in ethanol failed to achieve complete decontamination of the shell and membranes with resulting false positives when eggs were broken for culturing of the content. Dipping eggs for three seconds in boiling water resulted in complete destruction of Salmonella enteritidis in shells and membranes but sometimes caused the eggs to crack. A method of aseptically opening eggs without risk of contaminating the content from the shell or membrane was developed. Salmonella enteritidis deposited in/on the shell and membranes did not multiply during storage of the eggs at 20 degrees C for four weeks, the counts seemed to decrease. No Salmonella enteritidis was detected in the contents of any contaminated eggs.     

Effectiveness of electrolyzed water as a sanitizer for treating different surfaces

The effectiveness of electrolyzed (EO) water at killing Enterobacter aerogenes and Staphylococcus aureus in pure culture was evaluated. One milliliter (approximately 10(9) CFU/ml) of each bacterium was subjected to 9 ml of EO water or control water (EO water containing 10% neutralizing buffer) at room temperature for 30 s. Inactivation (reduction of > 9 log10 CFU/ ml) of both pathogens occurred within 30 s after exposure to EO water containing approximately 25 or 50 mg of residual chlorine per liter. The effectiveness of EO water in reducing E. aerogenes and S. aureus on different surfaces (glass, stainless steel, glazed ceramic tile, unglazed ceramic tile, and vitreous china) was also evaluated. After immersion of the tested surfaces in EO water for 5 min without agitation, populations of E. aerogenes and S. aureus were reduced by 2.2 to 2.4 log10 CFU/ cm2 and by 1.7 to 1.9 log10 CFU/cm2, respectively, whereas washing with control water resulted in a reduction of only 0.1 to 0.3 log10 CFU/cm2. The washing of tested surfaces in EO water with agitation (50 rpm) reduced populations of viable cells on the tested surfaces to < 1 CFU/cm2. For the control water treatment with agitation, the surviving numbers of both strains on the tested surfaces were approximately 3 log10 CFU/cm2. No viable cells of either strain were observed in the EO water after treatment, regardless of agitation. However, large populations of both pathogens were recovered from control wash solution after treatment.     

Shell rinse and shell crush methods for the recovery of aerobic microorganisms and enterobacteriaceae from shell eggs

Recovery of bacteria from shell eggs is important for evaluating the efficacy of processing and the quality and safety of the final product. Shell rinse (SR) techniques are easy to perform and widely used. An alternative sampling method involves crushing and rubbing the shell (CR). To determine the most appropriate method for recovering microorganisms from shell eggs, 358 shell eggs were collected from a commercial egg processor and sampled by SR and CR techniques. Total aerobic mesophiles and Enterobacteriaceae were enumerated on plate count and violet red bile glucose agar plates, respectively. Unwashed, in process, and postprocess eggs were evaluated in the study. Aerobic microorganism prevalence for eggshells sampled was similar for both methods (approximately 100%), but the log CFU per milliliter values were higher in the SR than the CR samples (3.2 and 2.2, respectively). Average Enterobacteriaceae recovery was similar for both methods (45 versus 40% for the SR and CR methods, respectively) when all eggs were considered together. This population was detected more often by SR when unwashed eggs were sampled (90 versus 56% for the SR and CR methods, respectively), equally by SR and CR for in-process eggs (30 versus 29.3% for the SR and CR methods, respectively), but more often by CR for postprocess eggs (10 versus 36% for the SR and CR methods, respectively). The SR technique was easier to perform and recovered larger numbers of aerobic organisms, particularly for unwashed eggs. However, the CR technique was more efficient for recovery of Enterobacteriaceae from postprocess eggs. Stage of shell egg processing may be an important consideration when choosing egg sampling methods.